Based on the experimental results--the trap distribution characteristic and flashover performance of Alumina ceramic samples in vacuum which were prepared by different ways, this paper try to discuss the relationship between the trap distribution and the flashover performance of Alumina ceramic sample. Comparing with the flashover performance of the insulator sam-pies in vacuum, it was found that the trap distribution could influence on the flashover performance. Based on our investigations, the relationship between the trap distribution and the flashover performance was discussed. It seems that the trap distribution maybe, the better parameter to reflect the flashover performance, and the further more works are needed to set up the relationship between the trap and the flashover.

A new set of facility for accelerated aging test of composite insulators has been developed at CEPRI (China Electric Power Research Institute). This paper mainly described the measurement and parameters monitoring system of this facility. This system can monitor total six channels current of insulator in real time, and it can also collect the corresponding information at the same time, such as the applied voltage, the environment parameters. Based on the collected data, the system can analyze and statistic the characteristics of the aged leakage current in time, and it can also save the important test data during the whole test procedure. In addition, this system has the capability of auto alarm, auto reset for the unexpected accidents during the test procedure. This system is a powerful system for the research on the aging performance of composite insulator.

In this paper, the influence of injected charge on streaming electrification of transformer oil has been investigated using a combined model. The experimental results reveal that there are relations between the injected charge, the charge density and the leakage current, and the polarity effect of injected charge exist in the influence on streaming electrification. The influence of injected charge is attributed to the interaction between the electric double layer and the injected charge. The effect of oil velocity on injected charge has been analyzed also.

It was considered that the trap distribution of alumina ceramics could affect the flashover performance of insulators. This paper investigated the trap distribution of alumina ceramic samples with different additives and different sintering temperature respectively. Experimental results show that the additives and sintering temperature play an important role on the trap distribution of alumina ceramics respectively, especially on the trap energy distribution, and they affect the trap distribution of alumina ceramics significantly.

In this study, the surface charge distribution on insulators in vacuum has been investigated under an impulse voltage (0.7/4μS) with a non-uniform field electrode system. The insulators studied were 99.9% alumina specimens with the shape of right circular cylinders about 5mm thick and 20mm in diameter. Using an electrostatic probe with shield in the form of capacitive voltage divider that was connected to an electrometer, the surface charge distribution on insulators were measured. The applied impulse voltage, and the corresponding current waveforms, the signal of luminosity were also observed during the voltage application. We investigated the surface charge distributions at different impulse voltage levels, at different shot number with a same voltage level, at the situations after a flashover occurred. Based on the experimental results, we found that the surface charge density on insulators is increased with the increase of the applied voltage, the shot number has a little influence at the same voltage level, and the charge density is decreased a lot after a flashover occurs. It's also found that the increase of charge density is often accompanied by the preflashover events.